In one type of analytical tool, a sample liquid is caused to move by capillary action. Such an analytical tool includes a capillary for producing a capillary force. To properly exert the capillary force onto a sample liquid, the inner surface of the capillary is hydrophilically treated. For example, in the structure shown in FIG. 9, a capillary 93 is formed by covering a groove 91 formed in a substrate 90 with a cover 92. In this case, the bottom surface 91a of the groove 91 and one surface 92a of the cover 92 are hydrophilically treated. The hydrophilization treatment with respect to the inner surface of the capillary 93 may be performed by ultraviolet irradiation, the application of a surface-active agent or plasma discharge such as glow discharge or corona discharge, for example. (See JP-A 2001-159618 and JP-A 2002-168821, for example.)
Recently, there is a tendency to reduce the sectional area of the capillary 93 to respond to the demand for the reduction of the amount of a sample liquid and the size reduction of an analytical tool. Particularly, in an analytical tool including a plurality of capillaries for analyzing a plurality of items, it is highly necessary to reduce the sectional area of each capillary. Since a typical analytical tool originally has a relatively small thickness, to effectively reduce the size of the analytical tool, the dimension of the tool as viewed in plan need be reduced. As shown in FIG. 10, to reduce the sectional area of each of capillaries 93 while reducing the size of the analytical tool as well, the width of each capillary 93 need be reduced. However, when the width of the capillary 93 is reduced to reduce the sectional area, the proportion of the hydrophilically-treated surfaces decreases in the case where hydrophilization treatment is performed only with respect to the bottom surface 91a of each groove 91 and to one surface 92a of the cover 92. Therefore, to properly move the sample liquid through the capillary 93, the hydrophilization treatment need be performed also with respect to the side surfaces 91b of the groove 91.
However, it is difficult to hydrophilically treat the side surfaces 91b of the groove 91 by the application of a surface-active agent or ultraviolet irradiation. Specifically, since light such as ultraviolet rays has linearity, it is difficult to cause ultraviolet rays to impinge on the side surface 91b of such a small flow path (groove) 91 as shown in FIG. 11A.
The hydrophilization treatment by the application of a surface-active agent is performed by supplying a liquid material containing a surface-active agent into the groove 91 and then drying the liquid material. Therefore, to apply the surface-active agent to the side surfaces 91b of the groove 91, it is necessary to completely fill the groove 91 with the liquid material and then dry the liquid material, as shown in FIG. 11B. In this way, since the groove 91 is filled with the surface-active agent to apply the surface-active agent to the side surface of the groove 91, the provision of a flow path having an intended sectional area is difficult.
The hydrophilization treatment by utilizing plasma discharge requires equipment for causing plasma discharge and hence requires high cost of equipment and manufacturing cost. Further, similarly to the hydrophilization treatment by ultraviolet irradiation, it is difficult to hydrophilically treat the side surfaces 91b of the groove 91 satisfactorily by plasma discharge.